1. Field of the Invention
This invention relates to improvement in and relating to a vehicle engine cooling flexible blade plastic fan assembly.
2. Description of the Prior Art
It has been proposed to manufacture the cooling fans from synthetic resin material for prevention of noises occasionally produced by metal blades and for simplicity in flattening the blades so as to increase the degree with an increase in rotational speed of the fan.
Difficulties were encountered, however, in preventing the connection between the plastic hub portion and a driving member from becoming loosened during the life due to the operating environmental temperature-variation therearound with the result that the engine-torque is not effectively transmitted to the fan assembly. This can be usually emphasized in certain applications to a truck engine which usually has the engine cooling fan coupled directly with the engine crank shaft having a higher tendency to conduct heat from the engine to the fan assembly.
It has been already proposed as a counter measure for the above-mentioned conventional drawbacks to employ an annular spacer member and a plurality of bushing, to provide a reliable coupling between the hub and the driving member by commonly passing the bushing, through the hub and the spacer member for bolting the hub portion to the driving member.
Further difficulties were encountered in that the above proposed method has not proven entirely sufficient.